Annual or biennial herbs to over 1 m tall with a tuberous tap root. Leaves hairy, stem clasping, lower ones with 1-4 pairs of lobes. Upper leaves more or less ovate to lanceolate. Flowers in clusters with the open ones overtopping or equalling the buds, bright yelow; spring to summer. Fruit mostly 3-7 cm long, valves with a pronounced midvein and a beak to 2 cm long.
A widespread weed.
A wide range of selections are used for salads and as vegetables, those of horticultural importance include the following, the list is likely to be extended as Asian vegetables increase in popularity:
Chinensis Group [B. chinensis L., B. rapa var. chinensis] Celery Mustard, Chinese White Cabbage, Chinese Mustard, Pak Choi, Choy Sum, Bok Choy. Leaves obovate, glossy in a tall cluster like a celery; stalks succulent and white.
Pekinensis Group [B. pekinensis (Lour.) Rupr., B. rapa var. pekinensis] Celery Cabbage, Chinese Cabbage, Pe-tsai, Wong Bok. Annual with the leaves large, soft and green. Perviridis Group [B. rapa var. perviridis] Tendergreen, Spinach Mustard, Komatsuna. Annual or biennial with the root crown thick and tuberous. Lower leaves soft, glossy green.
Rapifera Group Rapini, Turnip. Biennial. Leaves waxy blue on several stems from the crown, the lowermost deeply cut and stem clasping. Root swollen and of various shapes, flesh white or yellowish. The Turnip, sometimes listed as B. rapa subsp. sylvestris (L.) Janchen is well established as a weed of disturbed soils.
Ruvo Group Ruvo Kale, Italian Broccoli, Turnip Broccoli, Broccoli Raab. Leaves dark green, mostly glossy, lyre-shaped and deeply lobed.
Sarson Group Toria, Sarson. Leaves dark green.
Source: (1997). Brassicaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.